Conveyor belt having rotating drive shaft

ABSTRACT

An apparatus and method for processing products by chilling or freezing includes a conveyor for conveying the products along a plane of travel; lifting means disposed for intermittent contact with the conveyor during processing; cam means rotatable for contacting and displacing the lifting means to contact and displace the conveyor from the plane of travel, thereby displacing the products on the conveyor to prevent the products from adhering to the conveyor and other of the products; and drive means operatively associated with the cam means to impart rotational movement to the cam means for intermittently contacting and displacing the lifting means.

The present apparatus and method relate generally to the cooling andfreezing of food products.

A type of freezing for a product is individual quick-frozen (“IQF”). IQFfreezing of products provides products that are frozen, but not stucktogether. There are several known ways that IQF product is produced. Oneprocess is to simply freeze the products without allowing the same tocontact each other. This may be done by spacing individual product on afreezer belt or rack so they are not in contact with each other. In mostcases, this is not done for smaller products because it requires staffto arrange the product fed into the freezer and is an inefficient use ofmanpower and space, thus reducing capacity. Accordingly, as the piecesto become frozen become smaller, it becomes increasingly more timeconsuming and difficult to do.

With so-called tunnel freezers, the foods are conveyed continuously on aconveyor belt through a tunnel-like refrigeration space. Typically, aliquid/gas spray nozzle is situated in the tunnel-like refrigerationspace. The liquid/gas sprayed into the tunnel-like refrigeration spaceis distributed uniformly by fans. Additionally or alternatively, solidrefrigerant may be impinged onto the product. The foods conveyed throughthe tunnel-like refrigeration space are then cooled or frozen uniformlyon the conveyor.

Other methods of producing IQF products include fluidized beds, nitrogenimmersion or multi-pass tunnels. All of these allow for product to berandomly placed on a belt for freezing. Movement is created betweenadjacent pieces of product to prevent sticking, thereby creating IQF, tokeep pieces of product moving in relation to one another. For example,in nitrogen immersion, the pieces are not permitted to contact eachother when dropped into a nitrogen bath and are thereby frozen at thesurface of the bath before they can contact and adhere to one another.Multi-pass tunnels (including flighted tunnels) drop the pieces from onebelt to another repeatedly to break the product apart before it isfrozen solid. However, none of these methods is suitable for processingproduct contained in trays, since known methods would scatter the traysand displace the product from the trays.

In addition, different types of conveying equipment may be employedwhich are suitable for freezing processes. In many cases, companies makeboth IQF and tray types of products and attempt to have both processedwith the same equipment. Attempts to achieve this are done by removingor bypassing the IQF portion of the freezing line when tray productfreezing is desired. This typically requires relocation of equipment,and results in a reduction in production capacity due to the removal ofpart of the process line.

It is therefore desired to have the conveyor constructed and arranged tomove uninterrupted along the conveyed path of travel and not be removedfrom the process line.

Apparatus and method embodiments are provided for chilling or freezingproducts. It is understood that the following detailed description ofthe embodiments is exemplary, and is not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the apparatus and method embodiments and areincorporated in and constitute a part of this specification. Thedrawings illustrate various embodiments and serve to explain theapparatus and method, but are not intended as limitations.

FIG. 1 shows an apparatus for chilling and freezing different types ofindividual quick-frozen food products.

FIG. 2 shows an apparatus for chilling and freezing different types ofindividual frozen food products contained in trays.

FIG. 3 shows a portion of the conveyor and multiple cam wave axle withlifting bar of the apparatus of FIG. 1.

FIG. 4 shows a schematic of the wave axle cam disengaged from thelifting bar of the apparatus in FIG. 1.

FIG. 5 shows a schematic of the wave axle cam approaching for releasableengagement with the bearing surface of the lifting bar and the liftingbar in a partially raised position of the apparatus in FIG. 1.

FIG. 6 shows a schematic of the wave axle cam engaged to the bearingsurface of the lifting bar and the lifting bar in a fully raisedposition of the apparatus in FIG. 1.

FIG. 7 shows a schematic elevational view illustrating product beingconveyed along and displaced from the conveyor of FIG. 1.

FIG. 8 shows a schematic of the multiple cam wave axle with lilting barof the apparatus of FIG. 1.

FIG. 9 shows the left hand multiple cam wave axle.

FIG. 10 shows the right hand multiple cam wave axle.

FIG. 11 shows the left hand cam.

FIG. 12 shows the right hand cam.

FIG. 13 shows a partial view of a stepped region generally located onthe wave axle for mounting the cam.

DETAILED DESCRIPTION

Apparatus and method embodiments are provided for conveying foodproducts on a conveyer (i.e. belt) for processing through for example arefrigeration zone, such as a tunnel freezer. More specifically, theapparatus and method relates to a device wherein a wave-like motion isprovided to the conveyor to selectively displace the conveyor, and hencethe food products, along at least part of the conveyed path of travel toprevent the food products from adhering to the conveyor or to each otherduring freezing.

The apparatus and method for freezing products through a refrigerationzone, such as a tunnel freezer, includes conveying the product in such away so as not to disturb the product or products contained in a tray.Further, the apparatus and method selectively agitate product which isdisposed upon the conveyor to be individually quick frozen (IQF). Theapparatus is suitable for use in chilling and freezing food productssuch as for example, meat, chicken and seafood products. As used herein,cooling refers to a temperature reduction of a product to eitherchilling or freezing, depending on the total heat extraction from theproduct.

The apparatus provides a system for chilling or freezing products, andincludes a conveyor, such as a conveyor belt, that transports theproducts through refrigeration, such as mechanical refrigeration or arefrigerated medium for chilling or freezing the products, but with theadditional feature of actuating or agitating the conveyor, makingselective, intermittent contact with the conveyor and displacing theconveyor from its plane of travel, thereby displacing the products onthe conveyor during freezing to prevent products from adhering to theconveyor or to other products being conveyed. Agitation of the conveyorand injection of any refrigeration medium can take place in the same ordifferent zones.

The apparatus includes a multiple cam wave axle for displacing a liftingbar; a bearing surface mounted on the lifting bar; which is engaged bythe cam on the wave axle: and a conveyor, such as a conveyor belt, thattransports the products through a cooling or freezing apparatus, such asa tunnel freezer.

The apparatus can freeze and convey different types of food products,and in various product forms; so as not to adversely affect theintegrity of the product while being conveyed through the system. Thefood products may be IQF or non-IQF, and by way of example, raw orcooked, may require specific shape and orientation, may be breaded orunbreaded, marinated or unmarinated, or food products comprising anytype of coating.

The apparatus is flexible in that it can switch between IQF and non-IQFproducts, including but not limited to, products that can toleratelayering in the freezer, wherein they are conveyed and quick frozen bythe apparatus.

The apparatus and method may employ the total conveyor area forutilization of the capacity, without allowing food product to be removedfrom sections of the conveyor between the inlet and outlet of thefreezer housing and the freezing zone, regardless of the product/processtype. The freezing zone may comprise a single freezing zone or multiplefreezing zones wherein the temperature of the product is reduced toabout or below the freezing point of the product. The apparatus mayinclude one or a plurality of chilling or freezing zones.

In one embodiment of the apparatus, a wave-like motion is provided tothe conveyor by utilizing a multiple cam wave axle for displacing alifting bar, to contact and displace the conveyor. A bearing surface onthe lifting bar is engaged by the cam on the wave axle to displace thelifting bar.

In another embodiment of the apparatus, the wave-like motion is providedto the conveyor by utilizing a multiple cam wave axle for sequentiallydisplacing consecutive lifting bars, to contact and displace theconveyor upward in a forward or backward moving wave action on theconveyor belt. The bearing surface may include a lifting bar finger andthe multiple cams on the wave axle comprise cam lifting lobes (as shownin FIG. 8). The lifting bars are engaged by cams that are disposed in astaggered or intermittent pattern about the radius of the axle and alongits length.

The wave-like motion may be set such that the motion in the adjacentconveyor sections can be in phase, whereby a wave like motion is set upthrough the conveying system. Additionally, the frequency and theamplitude of the wave may be varied by adjusting the speed and thedegree of interaction between the conveying mechanism (e.g. belt) andthe multiple cam wave axle that controls the actions of the liftingbars. Alternatively, the frequency is variable, but the amplitude isfixed.

The wave-like, sinuous or undulating motion (for the sake of brevityhereinafter “wave-like motion”) provided through the conveying systemcan maximize the product surface area exposed to the refrigerationmedium, in which the refrigeration medium works either intermittently,simultaneously or continuously. In certain embodiments of the system,the wave-like motion is present either in part of or along the entirelength of the conveying section and the refrigeration equipment housing.In other embodiments, the wave-like motion is present so as to providethe conveying mechanism with alternating sections of non-wave sectionsfollowed by wave sections, or wave sections followed by non-wavesections, or in any desired arrangement.

The wave-like motion increases the heat transfer rates by maximizing theproduct surface area exposed to the refrigeration medium that isnormally not achieved when the product is touching other products orparts of the conveying mechanism. This results in more uniform heattransfer, leading to shorter freezing times, improved yields, higherproduct quality, and better cryogenic efficiency. A 50% to 100% increasein heat transfer rates and 25% to 50% decrease in dwell times may beachieved compared to existing freezing equipment.

Referring to FIG. 1, an apparatus embodiment of the invention is showngenerally at 10, and may be incorporated in a tunnel freezer. Theapparatus 10 includes a conveyor belt 12 to move product 14 through thefreezer housing 16. The conveyor belt 12 may be continuous as it passesthrough the length of the freezer housing 16. The housing 16, is cooledby mechanical refrigeration, carbon dioxide or nitrogen, or some othermeans using a refrigeration medium, including a combination of cryogenicand mechanical refrigeration techniques. In FIG. 1, a carbon dioxide ornitrogen spray outlet 18 provides the refrigeration medium.

As shown in FIG. 2, the apparatus 10 may also be constructed andarranged such that a wave axle 22 and lifting bars 26 are positionedaway from the conveyor belt 12 to permit the conveyor to moveuninterrupted along the plane of travel. This arrangement may be usedwhen the food product is placed in trays 44 as illustrated in FIG. 2.

Referring to FIG. 3, a wave generating assembly 20 is provided todisplace the product conveyed on the conveyor belt 12 to permit an IQFfreeze. The conveyor belt 12 may be constituted of stainless steel andmay move on slideways of synthetic material secured to the frame 28.Belt 12 is secured in guides that permit differential expansion betweenthe steel and the synthetic material without hindrance and withoutdeformation of the slides. The drive motor (not shown) of conveyor belt12 may be mounted on the frame 28 and may drive the conveyor belt bymeans of sprockets or other known drive devices, the tension of the beltand its differential elongation being compensated by known auxiliarydevices.

The wave generating assembly 20 includes the wave axle 22 with multiplecams 24 for displacing a lifting bar 26. The wave axle 22 may besupported on the frame 28 adjacent to the conveyor belt 12 extending ina direction parallel to the center of conveyor belt 12 on both the leftand right hand sides of the conveyor. The wave axle 22 may be driven bya motor 66 via gears 56, 58 attached to a drive shalt 54 powered by themotor, and to the wave axle 22, respectively.

Other wave axles 22, as shown in FIGS. 9 and 10, may be mounted on theleft side (FIG. 9) of the conveyor belt 12 and on the right side (FIG.10) of the conveyor belt 12 along its length. The wave axles aresubstantially similar in design, but those on opposite sides of theconveyor belt comprise opposite hands. The wave axles may have generallystepped regions 30 (FIG. 13) equally located along its length. In anillustrative arrangement, eight (8) cams 24 are mounted on each of theleft side and right side wave axles 22.

Cams 24 are generally located in the stepped regions 30 on the wave axle22 and are arranged in a staggered formation along the axle 22. Separatecams 24 are mounted on the wave axle located on the left side (FIG. 11)of the conveyor belt 12 and on the right side (FIG. 12) of the conveyorbelt 12. The cams 24 are similar in design but opposite hands (FIGS. 11and 12). In an exempletive arrangement, eight (8) cams 24 are mounted oneach of the left side and right side wave axles 22 and may be secured tothe wave axle by fasteners such as set screws, for example. M6×30.

Both the cams 24 and the wave axles 22 may be made from a stainlessaustenitic chromium-nickel steel material, for example, SAE 304, due toits good corrosion resistance and weldability.

Referring now to FIGS. 4-6, a bearing surface 32 formed on the liftingbar 26 is engageable with the cam 24. These figures show the lifting bar26 displaced by the cam 24 in a series of positions in relation to thelifting bar's starting point and maximum lift point.

FIG. 4 illustrates the condition where the lifting bar 26 and the cam 24are in a lowered or non-engaged position.

FIG. 5 illustrates the cam 24 rotated 90 degrees toward the bearingsurface 32 to engage same to elevate the lilting bar 26 and begin toaccelerate and elevate the belt (not shown) to its maximum position.

FIG. 6 illustrates the cam 24 rotated 180 degrees from its initialposition and in full engagement with the lifting bar 26 resulting in thebelt (not shown) moved to its uppermost position. This rapid movement ofthe belt will cause the pieces of food product to be displaced from orprojected off of (above) the belt for a short duration.

As shown in FIG. 7, the belt 12 will conform substantially to thecontour of the lifting bar 26. The center portion of the lifting bar 26will have the greatest movement and thus will project the product orproducts 14 in this vicinity the highest off of the belt 12. As seen inFIG. 7, the pieces of the product 14 may have a trajectory that is inpart a combination of the “Y” component indicated by arrow 34 and a “Z”component indicated by arrow 36. The food product 14 may be projectednot only upwardly from the belt (“Y” component) and along the traveldirection of the belt 12 (“Z” component) but may be laterally displaced.i.e. it may have an “X” component as indicated by arrow 38 in FIG. 7.The trajectory of the pieces 14 will displace the products from eachother on the conveyor during chilling or freezing and prevent theproducts from adhering to the conveyor or other of the products duringchilling or freezing.

In an alternative embodiment of the apparatus 10, as shown in FIG. 8,the bearing surface includes a lifting bar finger 40 extending from thelifting bar 26, and the multiple cams on the wave axle 22 include camlifting lobes 42. In one embodiment, the lifting bar finger 40 isattachably disposed below an extension 60 of the lifting bar 26. Thelifting bar extension 60 extends through a slot 64 of displacementcontrol member 62, which in part defines the range of movement of theextension 60 and the lifting bar 26 in the Y-component direction. Theextension 60 and lifting bar 26 are at their lowest point when thelifting bar finger 40 is disengaged from the cam lifting lobe 42. Atthis point, the lifting bar 26 may be disengaged from contact with theconveyor 12. When the lifting bar finger 40 engages the cam lifting lobe42, the lifting bar finger 40 is displaced upward, causing the liftingbar 26 to engage and move the conveyor belt 12 upwards, until maximumdisplacement of the belt 12 is reached due to the extension 60 beingelevated to its highest point within the slot 64 of the control member62, and with the cam lifting lobe 42 in full engagement with the liftingbar finger 40. When consecutive cam lifting lobes 42 along the multiplecam wave axle 22 engage their corresponding lifting bar fingers 40 asthe wave axle is rotated, the lifting bars 26 are lifted in sequence tocontact and displace the conveyor 12 and to impart the wave-like motionto the conveyor belt 12.

In one embodiment, when products for which displacement is not desiredare processed in the freezer (e.g., for products in trays 44, FIG. 2),disengaging the lifting bar 26 from the conveyor belt 12 ceases thedisplacement. When displacement is desired, the lifting bar 26 contactsthe conveyor belt 12 when actuated and moved to a position where thebars 26 intermittently contact and displace the conveyor belt 12.Circulation means such as fans 46 may be used to enhance heat transferin either IQF or tray mode of operation.

In a further embodiment, the conveyor belt 12 is disposed at an angle tothe horizontal and may comprise multiple conveyor sections, withtransfers of product between the sections. Each section can be actuatedor non-actuated as desired by the apparatus 10.

On the conveyor belt 12 may be a retaining means (not shown) forretaining products on the conveyor belt 12. These retaining means aregenerally known to those skilled in the art, and include, for example,projections raised above the top surface of the conveyor belt 12.Adjacent to the conveyor belt 12 may be means to retain (not shown) theproduct being displaced on the surface of the conveying mechanism, whilethe product is traveling through the equipment housing. Such retainingmeans can include belt side clips (not shown) which may be 3 inches (75mm) high for example, and are part of the conveyor belt 12.

In certain embodiments, the wave generating means may includeself-propelling mechanisms to effectuate movement of the lifting bar 26without outside power.

Referring again to FIG. 2, the process may include estimating theproduct heat load so as to control the degree of cryogen injection. Oneembodiment utilizes a weigh scale or a laser or other optical measuringmeans that estimates/calculates the volume/weight of the product, orother characteristics of same, so as to control the amount of injectionof the refrigeration medium necessary for that product. This embodimentmay use a sensor 48 to sense the throughput of the product, the sensorutilizing a controller 50 to actuate the valve 52, which controls theamount of cryogen injection.

The agitation and the injection of any refrigeration medium may takeplace in the same freezing zone or in different freezing zones. Thetemperature established in the freezing zone may be isothermal,co-current or counter-current. Convective processes may be used todisperse the refrigeration medium uniformly in the freezing zone forbetter heat transfer. Such processes can utilize, but are not limitedto, fans, impingement or directed gas jets to disperse the refrigerationmedium.

The freezer apparatus embodiment 10 and method permit a user toconsolidate separate freezer lines (of IQF and trayed products) by beingable to switch or alternate between the “vibratory” mode and thenon-vibrating or “tunnel” mode.

The present embodiments have a compact design which provides increasedspace in a tunnel freezer for cryogen application use, by eliminatingchain and sprocket drives placed at the cam shaft ends for an agitationsystem assembly to agitate or vibrate the product conveyed on theconveyor belt to produce an IQF freeze.

The apparatus and method ensure that frozen food products will notadhere to one another, the conveyor or the tray transporting the foodproducts during freezing.

In certain embodiments an apparatus for conveying food products to beprocessed, includes conveying means for conveying the food productsalong a path of travel for processing; lifting means operativelyassociated with the conveying means for displacing the conveying meansvertically from the path of travel at select intervals; cam meansadapted for rotation to contact and impart a lifting force to thelifting means at the select intervals for providing an undulating motionto the conveying means at the select intervals; and drive meansconnected to the cam means for transmitting a drive force to the cammeans for rotational movement of the cam means. The lifting means mayinclude at least one longitudinal member having a bearing surface, andthe cam means may include at least one shaft member having at least oneprotrusion extending therefrom for intermittent contact with the bearingsurface at the select intervals. In one embodiment, an apparatus isprovided for conveying products to be chilled or frozen without saidproducts adhering to the apparatus or other products, comprising: aconveyor for transporting the products along a path of travel throughrefrigeration for chilling or freezing the products; a lifting bardisposed below and proximate to the conveyor for selective, intermittentcontact with the conveyor to displace the conveyor from a plane oftravel, thereby displacing the products on the conveyor to prevent theproducts from adhering to the conveyor or other of the products; a wavegenerating assembly adapted for rotation and having a cam arrangementfor transversely oriented rotation relative to the path of travel fordisplacing the lifting bar at a lateral side relative to said path; abearing surface on the lifting bar releasably engageable with the camarrangement to displace the lifting bar to contact and displace theconveyor from the plane of travel; and drive means operativelyassociated with the wave generating assembly to rotate the camarrangement for intermittently displacing the lifting bar.

In one embodiment, the cam means comprises a first shaft member disposedat a first side of the conveying means and having a first plurality ofprotrusions extending therefrom in a staggered arrangement along alength of the first shaft member, and a second shaft member disposed ata second side of the conveying means opposite to the first side andhaving a second plurality of protrusions extending therefrom in astaggered arrangement along a length of the second shaft member, thefirst and second plurality of protrusions co-acting with the liftingmeans at the select intervals for displacing the lifting means to impartan undulating motion to the conveying means.

In one embodiment, an apparatus for conveying products to be chilled orfrozen without said products adhering to the apparatus or other productsincludes a conveyor for transporting the products through refrigerationfor chilling or freezing the products; a lifting bar disposed below andproximate to the conveyor for selective, intermittent contact with theconveyor to displace the conveyor from a plane of travel, therebydisplacing the products on the conveyor to prevent the products fromadhering to the conveyor or other of the products; a wave generatingassembly adapted for rotation and having a cam arrangement fordisplacing the lifting bar; a bearing surface on the lifting barreleasably engageable with the cam arrangement to displace the liftingbar to contact and displace the conveyor from the plane of travel; anddrive means operatively associated with the wave generating assembly torotate the cam arrangement for intermittently displacing the liftingbar.

In certain embodiments a method for processing food products includesconveying products for processing on a conveyor, supporting the conveyoralong a path of travel, rotating a wave generating means proximate theconveyor; contacting the wave generating means intermittently with theconveyor for displacing the supported conveyor and products along atleast a portion of the path of travel to prevent the products fromadhering to the conveyor and other of the food products on the conveyorduring processing. In one embodiment, an apparatus is provided forconveying food products to be processed, comprising conveying means forconveying the food products along a path of travel for processing;lifting means operatively associated with the conveying means fordisplacing the conveying means vertically from the path of travel atselect intervals uniformly across a width of the conveying means; cammeans adapted for transversely oriented rotation to contact and impart alifting force to the lifting means at a lateral side relative to saidpath and at the select intervals for providing an undulating motion tothe conveying means at the select intervals; and drive means connectedto the cam means for transmitting a drive force to the cam means forrotational movement of the cam means.

It will be understood that the embodiments described herein are merelyexemplary, and that one skilled in the art may make variations andmodifications without departing from the spirit and scope of theinvention. All such variations and modifications are intended to beincluded within the scope of the invention as described and claimedherein. Further, all embodiments disclosed are not necessarily in thealternative, as various embodiments of the invention may be combined toprovide the desired result.

1. An apparatus for conveying products to be chilled or frozen withoutsaid products adhering to the apparatus or other products, comprising: aconveyor for transporting the products along a path of travel throughrefrigeration for chilling or freezing the products; a lifting bardisposed below and proximate to the conveyor for selective, intermittentcontact with the conveyor to displace the conveyor from a plane oftravel, thereby displacing the products on the conveyor to prevent theproducts from adhering to the conveyor or other of the products; a wavegenerating assembly adapted for rotation and having a cam arrangementfor transversely oriented rotation relative to the path of travel fordisplacing the lifting bar at a lateral side relative to said path; abearing surface on the lifting bar releasable engageable with the camarrangement to displace the lifting bar to contact and displace theconveyor from the plane of travel; and drive means operativelyassociated with the wave generating assembly to rotate the camarrangement for intermittently displacing the lifting bar.
 2. Theapparatus according to claim 1, wherein the cam arrangement comprises awave axle having a plurality of cams disposed in a staggered patternabout a radius and a length of the wave axle.
 3. The apparatus accordingto claim 2, wherein the wave generating assembly disposed at one side ofthe conveyor is of opposite hand to the wave generating assemblydisposed at an opposed side of the conveyor.
 4. The apparatus accordingto claim 3, wherein each of the plurality of the cams on the wave axlecomprises a lilting lobe.
 5. The apparatus according to claim 4, whereinthe bearing surface comprises a lifting bar finger.
 6. The apparatusaccording to claim 5, wherein the lifting bar finger is connected to anddisposed below an extension of the lifting bar.
 7. The apparatusaccording to claim 6, wherein the lifting bar extension is adapted fordisplacement through a range of motion to define a range of movement forthe lifting bar extension and the lifting bar.
 8. The apparatusaccording to claim 1, wherein the drive means comprises a motor.
 9. Theapparatus according to claim 1, wherein the lifting bar is adapted to bepositioned away from and out of contact with the conveyor foruninterrupted movement of the conveyor along the plane of travel. 10.The apparatus according to claim 1, wherein the conveyor comprises atleast one wave action section and at least one non-wave action section.11. The apparatus according to claim 1, wherein the products are foodproducts.
 12. An apparatus for conveying food products to be processed,comprising conveying means for conveying the food products along a pathof travel for processing; lifting means operatively associated with theconveying means for displacing the conveying means vertically from thepath of travel at select intervals uniformly across a width of theconveying means; cam means adapted for transversely oriented rotation tocontact and impart a lifting force to the lifting means at a lateralside relative to said path and at the select intervals for providing anundulating motion to the conveying means at the select intervals: anddrive means connected to the cam means for transmitting a drive force tothe cam means for rotational movement of the cam means.
 13. Theapparatus according to claim 12, wherein the lifting means comprises atleast one longitudinal member having a bearing surface, and the cammeans comprises at least one shaft member having at least one protrusionextending therefrom for intermittent contact with the bearing surface atthe select intervals.
 14. The apparatus according to claim 12, whereinthe cam means comprises a first shall member disposed at a first side ofthe conveying means and having a first plurality of protrusionsextending therefrom in a staggered arrangement along a length of thefirst shall member, and a second shaft member disposed at a second sideof the conveying means opposite to the first side and having a secondplurality of protrusions extending therefrom in a staggered arrangementalong a length of the second shaft member, the first and secondplurality of protrusions co-acting with the lifting means at the selectintervals for displacing the lifting means to impart an undulatingmotion to the conveying means.